Widely used recommendations developed by the American Petroleum Institute for the identification of different products in storage, and for identification of the storage equipment used for different fuels.

The system involves use of different colors and distinctive markings to identify specific products. The color code is used at terminalsbulk plants, and retail motor fuel outlets.

The purpose of using a uniform color code is to prevent mix-ups in the delivery of petroleum products – to prevent diesel fuel, for example, from being dropped into a gasoline storage tank, or to prevent gasoline from being dropped into a monitoring well. The color code is used for marking manhole covers in retail outlets.